Failure analysis of a 24 T crane hook using multi-disciplinary approach

Abstract

Crane hooks are the safety–critical component which are extensively used for material handling in manufacturing units. Any failure of such component may lead to casualty in workplace apart from loss of productivity. Current work presents analysis of a failure of 24 T crane hook using multi-disciplinary approach involving perspective of on-site observers, metallurgical investigation and finite element analysis.Analysis consisted of visual observations, dimensional checking, micro and macro fractography using scanning electron microscope and stress analysis using analytical calculation as well as finite element (FE) modelling using ABAQUS® 2018 version. Failure of the hook occurred from the threaded root near the step which is a potential stress concentration site. Deep tool marks were observed which can increase the stress concentration factor to initiate fatigue cracks. Presence of finely spaced striation marks confirmed fatigue mode of failure under low stress. The role of metallurgical abnormalities like non-metallic inclusions has been discussed. Finite element simulation for crane hook confirmed that the failure occurred from the region of maximum stress. Furthermore, stress intensification due to surface irregularities (notch in the present case) is also explained using FE simulations. Stress concentration at threaded root portion due to notch is estimated for different sizes of notches and the trend of stress concentration with notch size is explained. Recommendations are made to prevent similar failure to occur in future.